Optical fibers are normally constructed with a protective outer coating, which is frequently acrylate or another plastic material. The coating material is typically applied to the fiber during manufacture while the coating is still tacky. The coating may be subsequently cured by ultraviolet light to form the coated fiber. A jacket may be provided around one or more coated fibers for protection. Prior to splicing the optical fibers, the ends of two optical fibers to be spliced together need to be stripped of their protective coating and cleaved to provide an accurately sheared end surface for mating.
Existing stripping devices include a hand-held stripping device as shown in FIGS. 1-3, and is commercially available through the Miller Tool Division of Ripley Company of Cromwell, Connecticut. This hand-held tool 1 includes a pair of levers 2 pivotally attached to each other about an axis provided by a screw and nut assembly 3. Each lever 2 has a flat side which interfaces with the flat side of the other lever in a manner similar to a pair of scissors. A triangular shaped cutout portion 4 is provided in each lever 2 adjacent its forward end. The triangular shaped cutout portions 4 have a beveled surface 5 facing away from the opposing lever 2. A spring 6 is mounted at each end to a respective lever 2 to bias the levers 2 into an open position. A set screw 7 projecting from a rivet on one lever 2 engages a side surface 8 on the opposing lever to serve as a stopping arrangement that limits their relative movement in the direction that the handle portions 9 of the levers 2 are moved toward each other. In the maximum closed position, the triangular cutout portions 4 form a diamond shaped opening dimensioned so that the fiber of a properly centered coated fiber could tightly fit inside the diamond. In operation, a coated fiber is inserted perpendicularly into the cutting tool adjacent the triangular cutout regions 4, and the levers are pivoted against the force of the biasing spring 6 causing the beveled surface 5 on one lever 2 and the flat edges of the other lever 2 to cut into the coating of a coated fiber. Holding the fiber steady, the user slides the tool towards the free end of the cable causing the beveled surfaces and edges to scrape off the coating in fragments. It is noted that while the lever 2 with the flat edge facing the free end of the cable will tend to push the coating off of the fiber and the beveled surfaces 5 of the other lever 2 will tend to scrape the coating off of the fiber, the overall effect of this process with this tool 1 is one of scraping the coating off in fragments.
However, this type of striping tool has significant drawbacks. As the fiber is pulled through the beveled surface 5 and the opposing edge, the cutting edges can come into contact with the fiber and scratch it and/or kink it. Other strippers operate on the theory of scraping and are also highly susceptible to scratching the fiber. Moreover, microscopic alignment and tolerancing errors can also cause the fiber to be scratched. This can be significant as one small scratch in the fiber can reduce its strength by up to 90%. Hand-held stripping units lack exceptional stability which can result in misalignment between the fiber and the stripping edges and cause scratching of the fiber.
Attempts to solve these drawbacks have not been entirely successful. U.S. Pat. No. 5,033,335 to Yatsu et al. discloses the use of a heating element which applies direct heat to a clamped free end of the coated fiber. The heating element is intended to soften the coating. However, merely softening the coating does not solve the problem of scratching. Moreover, the combination of clamping the free end of the fiber and applying direct heat can damage the fiber. Additionally, the fact that the stripping blade surface does not extend entirely around the circumference of the coated fiber makes the stripping process less than optimal.
U.S. Pat. No. 4,971,418 to Dorsey et al. attempts to overcome these problems by stripping the coating off of the fibers by using a combination of an acid and a laser to melt away the coating. However, this is a costly process which has drawbacks beyond its cost, they include the generation of toxic waste and the exposure of potentially hazardous material to the operator. Accordingly, a solution that overcomes the drawbacks of the prior art was thus necessary.